The U.S. State Department's top expert on war crimes issues is welcoming Serbia's arrest of former Bosnian-Serb leader Radovan Karadzic, and says it bodes well for the Belgrade government's future in Europe. Ambassador Clint Williamson says the arrest should be worrisome for former Bosnian-Serb military chief Ratko Mladic, who is still at large. VOA's David Gollust reports from the State Department.

Karadzic, indicted by the International Criminal Tribunal for the former Yugoslavia on charges of genocide and crimes against humanity, was considered Europe's most- wanted man.

His apprehension in Serbia after 13 years on the run was especially satisfying for Williamson, the U.S. Ambassador-at-Large for War Crimes Issues - a career federal prosecutor who worked on the Yugoslavia tribunal staff for seven years.

In an interview with VOA, Williamson said the four-year war in Bosnia-Herzegovina which began in 1992 was very much driven by the agenda of Karadzic, who used a campaign of ethnic cleansing against Muslims and Croats to stake out his Serb mini-state:

"He set up detention camps were people were kept in just the most horrible conditions, engaged in the siege of Sarajevo, where shells were continuously poured into the city, where snipers fired on civilians trying to go about their daily business," said Clint Williamson. "And then throughout the country there were many, many episodes of mass killings, where forces under his command attacked civilians and in order to drive them out, to eliminate their presence, just killed them by the thousands."

The arrest of Karadzic came just days after a commemoration in Bosnia - attended by Williamson - of the most notorious single criminal act of the war, the 1995 massacre of some eight thousand Muslim men and boys at Srebrenica, a U.N. safe area overrun by Serb forces.

The U.S. envoy said NATO forces who intervened to end the war in 1996 probably had chances to capture Karadzic early-on but failed to do so and he went underground - hiding in Bosnia and later Serbia, presumably with some measure of official protection.

Williamson said the turning point in the case was clearly the assumption of power earlier this month of a new pro-Western government in Belgrade, which he said stands to benefit politically from arresting Karadzic and turning away from the country's violent recent past.

"His arrest is going to have a huge impact," he said. "Serbian integration into the EU, into NATO has been stalled by the fact they have not been cooperative with the war crimes tribunal in the Hague, that they had not done everything that they could have to address these outstanding issues and in particular the arrest of fugitives. So the fact they now have arrested one of the biggest-name fugitives, this I think is going to reflect very well on them."

The arrest of Karadzic leaves only his former military chief Ratko Mladic and another senior official of the Bosnian Serb enclave, Goran Hadzic, still at large. Williamson said Monday's arrest must be unsettling for Mladic, the alleged trigger-man for the Srebrenica killings.

"He's got to be a very nervous man today," said Williamson. "He also has been able to rest comfortably, I'm sure, thinking that the Serbian government was not going to move against him, and all that he had to do was remain in hiding and just tough it out a little bit longer, and that eventually the tribunal would close and he would be free. So I think this is a very worrying sign for him and for those who support him."

The Hague tribunal was to have completed its trials by the end of this year and all appeals of cases by 2010.

Williamson says he is confident of a consensus among member countries of the U.N. Security Council to extend the mandate as long as necessary to complete the Karadzic trial and remaining cases.